Mechanical waves are waves that require a medium. This means that they have to have some sort of matter to travel through. These waves travel when molecules in the medium collide with each other passing on energy. One example of a mechanical wave is sound. Sound can travel through air, water, or solids, but it can't travel through a vacuum. It needs the medium to help it travel. Other examples include water waves, seismic waves, and waves traveling through a spring.
Hi Kelly, I'm now 28 weeks pregnant with twins and I first started feeling them move when I was around 15/16 weeks pregnant but this is my second pregnancy. In my first pregnancy (not twins) I didn't feel any movement until I was 24 weeks pregnant. I think everyone feels their babies at different times so don't worry about anything.
According to Gillespie, you may feel a strong kick or punch, a rolling sensation as your baby turns over or shifts position or a rhythmic tapping feeling that is most likely your baby having the hiccups. When You Will Feel Your Baby's Movements. Your baby will begin to move around sometime during your second month of pregnancy, reports Gillespie. You will not be able to feel these movements because your unborn baby is still far too small for you to detect his movements.